Bumping this topic to say that I just finished Red Dead Redemption a few minutes ago. In the "What are You Currently Playing" topic, I said I was about 3/5 through the main story, but I turned out to be completely wrong: I only had about 5 or 6 missions left when I made that post
It certainly ended quicker than I thought it would.
As for the ending, I will absolutely
NOT give it away, but it left me unsatisfied for two reasons (that, again, I will not spoil. It will make sense when you finish the game).